1. Field of the Invention
The present invention relates to a method of data backup for a storage system via a Storage Area Network (SAN), and is especially applicable to the comprehensive backup of data in a plurality of storage systems whose interfaces are different from each other or data which is managed by different operating systems.
2. Description of Related Art
Previously, an individual host computer was connected to each backup device such as magnetic tape storage and this host computer performed the backup of storage data. In mainframe computer systems, because the importance of backup has long been recognized, an operation and management environment for backup processing by highly functional backup utility programs or other means has been established. On the other hand, in recent years, also in open systems such as UNIX (UNIX is exclusively licensed by X/Open Company Ltd. and is a registered trademark in the U.S. and other countries) and Windows (Windows is a registered trademark of Microsoft Corp. in the U.S. and other countries), due to the increased storage capacity of storage systems, the efficient backup of data in disk storage has become an important issue. Especially, in enterprises constructing large-scale computer systems, because mainframe systems and open systems exist and are operated together, it is desirable to be able to backup both systems with the same backup device using the same backup utility program.
For open systems, the construction of storage systems that use a Storage Area Network (SAN) is currently in the spotlight. Specifically, this system uses a fiber channel (FC) in the disk interface and is configured with a plurality of host computers and fiber channel disk units connected via a fiber channel switch or hub. Here, a fiber channel disk unit is a disk unit that has a FC interface. SCSI commands can be mapped onto the fiber channel protocol. Moreover, the fiber channel disk unit can also interpret and execute the SCSI commands mapped onto that protocol, even if the interface is changed to FC. For this reason, the OS or application program running on the host computer can perform operations for the disk unit with SCSI commands that are widely used for accessing to disk units.
On the other hand, the issue of backing up data for an open system in a mainframe system is disclosed in Japanese unexamined patent gazette H10-283272, which is corresponding to U.S. application Ser. No. 09/52985. Disclosed in said gazette is a means of backing up data by connecting the disk control units of a mainframe system and open system with a communication channel, and accessing the disk control unit of the open system from the mainframe.
However, in the means disclosed in Japanese unexamined patent gazette H10-283272, since a one-to-one communication channel connects the disk control unit of the mainframe system and disk control unit of the open system, the disk control units of both the mainframe system and the open system must be provided with an interface for said communication channel separate from each interface to their hosts. Moreover, the issue of how to transfer data using this communication channel is also not disclosed in said gazette. Further, the specific method of conversion between the variable length recording method that a file system on the mainframe uses and the fixed length recording method that a file system on the host of the open system uses is also not disclosed. Also, data backup in a SAN environment is not considered by said gazette.
To accurately perform backup, cooperation with the application program must be considered. In other words, while an application is running, care must be taken when backing up or restoring data which the program refers to or updates. This is because while backup is being performed, the data that is the object of the backup may be partially modified by the application program. In this case, the backup data will become inconsistent data and it is meaningless to restore this data. This state is called the inconsistent state of backup data. In Japanese unexamined patent gazette H10-283272, a means to avoid this type of inconsistent state is not considered.
Therefore, the object of the present invention is for the OS and program running on the mainframe host to be able to access the contents of the open system storage with a method similar to the one for the storage of the mainframe system. And as such, the contents of the open system storage can be backed up on the mainframe system.
Another object of the present invention is to provide a means, while the application program is running on the open system host, to backup in a consistent state, the data referenced by that application.
The disk control unit of the mainframe system is provided with a means such as a fiber channel for accessing storage on the SAN and a means of converting the I/O data format of the storage. Thus, the mainframe system host connected to said disk control unit can be made to access the storage volume of said SAN in the same manner as a volume under the disk control unit of the mainframe system. Moreover, the I/O control processor of the mainframe system host may be equipped with a means of accessing storage on the SAN and a means of converting the I/O data format of the storage. Thus, also the mainframe can be made to access the storage volume on said SAN.
Further, by providing a means of communication between the program on the mainframe system host and the program on the open system host, consistency of the backup data is maintained.